<!DOCTYPE html>
<html lang="en">
<head>
    <meta charset="UTF-8">
    <title>斐波那锲数列</title>
</head>
<body>

<script>
    function fn(n) {
        if (n == 1 | n == 2) {
            return 1;
        }
        return fn(n - 1) + fn(n - 2);
    }
    var n = parseInt(prompt('输入一个数字'));

    console.log(a3);
</script>

</body>
</html>